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Re: work in progress on dual-use theory

From: Nathan <nathan@webr3.org>
Date: Fri, 21 Jan 2011 20:56:01 +0000
Message-ID: <4D39F2E1.7040606@webr3.org>
To: Jonathan Rees <jar@creativecommons.org>
CC: AWWSW TF <public-awwsw@w3.org>
Jonathan Rees wrote:
> So I'm making a model of the web in which all info-resources are
> 'fixed resources' (Tim's term).  I figure that if we can't spin a solid
> story around this, the whole enterprise is hopeless.  I think the following
> is pretty good, except for a gaping hole (inconsequential I think)
> around exactly which resource is 'at' a URI. This goes back to our
> 'phlogiston' discussion.
> Without 'phlogiston' the theory becomes immensely simpler, but TimBL
> has imposed this as a requirement and shown little flexibility around it.
> Jonathan
> Term: 'directive' (class)
>   Def: Information supplied in addition to content that is
>   intended to direct the interpretation of the content.  Content-type
>   header or equivalent, content-language or equivalent, perhaps
>   others.  (Expires: header??)
>   Definition source: invention of JAR
>   Similar to: metadatum, HTTP entity header

is compression a factor?

> Term: 'fixed resource' (class)
>   Def: Content + directives, produced through some real process
>   but with identity generic across physical incarnation.  I.e. it can
>   be incarnated in multiple locations (disk drives, etc), each of
>   which might be said to hold a copy of the fixed resource.
>   Definition source: TimBL genont

assume fixed resource doesn't have any properties which vary over time?

must directives be maintained? are these the same fixed resource?


this one too?


> Term: 'representation' (class)
>   Def: Similar to 'fixed resource' but independent of provenance.
>   That is, the identity of a 'representation' is determined by the
>   content and directives.  In case two processes coincidentally result
>   in the same content and media type, we would say there are two fixed
>   resources but that the two fixed resources 'have' the same
>   representation.
>   Similar to: RFC 2616 'entity', AWWSW 'representation'
>   Note: JAR and Pay Hayes both oppose making a distinction betwen
>   fixed resource and representation.  The distinction is included at
>   TimBL's insistence.

if fixed resource consists of only content + directive, and all the 
properties are identical, how would you ever know they were different in 
the first place? One must first be able to determine you have two 
distinct things - I may be missing something here.

> Term: 'has fixed representation' (property)
>   Domain: fixed resource
>   Range: representation
>   Functional.
>   Def: The representation is a projection of the fixed resource,
>   i.e. shares its content and directives.
> Term: 'is authorized for' (data property)
>   Domain: 'representation'
>   Range: URI (xsd:anyURI)
>   Def: The agent that legitimately controls the URI (its "owner")
>   authorizes the representation for inclusion in an HTTP 200 response
>   to a GET request with the URI as target URI.
>   Definition source: HTTPbis part 1 section 2.6.1
>   http://tools.ietf.org/html/draft-ietf-httpbis-p1-messaging-12#section-2.6.1

if we're still in the domain of HTTPbis here...
- assuming 203 Non-Authoritative Information comes in to play here?
- Content-Location which differs in domain or scheme?

> Term: 'is served fixedly from' (data property)
>   Domain: 'fixed resource'
>   Range: URI
>   Def: R is served fixedly from U iff R's representation is the only
>   representation authorized for U.
>   Similar to: log:URI ?

define R?

I've been trying to find a way to prove that one and only one 
representation exists for U (using httpbis) and can't - does that affect 
anything? (I can provide a list of every case where I thought it may be 
possible to assert this, and the reasons why it can't be asserted)

>   Note: 'is served fixedly from' is not functional under this definition.  If
>   R is served fixedly from U then so is any fixed resource S that has
>   the same representation.
> Now we can stipulate that fixed resources, or at least some of them,
> can act as subjects of metadata, by interpreting the content
> (as modulated by the directives) appropriately.  In particular:
> - RDFS - can participate in rdfs:seeAlso, rdfs:isDefinedBy, etc.

does that follow?

> - FOAF  - every fixed resource is a foaf:Document, so can participate
>   in foaf:homepage, foaf:topic, etc.

so foaf:Document is the class of all fixed resources?

> - Dublin Core  - fixed resources can have dc:creators, etc.

can have dc:hasPart & dc:isPartOf? dc:modified? (fixed resource can be 

> - CC REL - some fixed resources are legally protected by copyright
>    and can be licensed (xhtml:license property)
> We can express a form the httpRange-14 rule:
>   When exactly one representation is authorized for U,
>   (a) everyone is urged to use U to name only some particular fixed
>   resource served fixedly at R (which one is not clear, but probably
>   depends on the process by which it was created or chosen by U's
>   owner),
>   (b) absent information about which fixed resource is involved,
>   just assume that U names some unknown fixed resource served fixedly
>   at R.

so conneg would be impossible, if I read correctly?

generally, I'm reading this as, every fixed resource is 1-1 with a 
single "representation" from the time of creation till the end of time. 
is that correct?


Received on Friday, 21 January 2011 20:57:16 UTC

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